Editorial Feature

Gregoryite – Occurrence, Properties, and Distribution

Gregoryite was named after Professor John Walter Gregory (associated with the University of Melbourne, Australia and the University of Glasgow, Scotland), and was discovered in 1980.

Properties of Gregoryite

The following are the key properties of gregoryite:

  • Cell Data
    • Space group: P63mc (synthetic)
    • a = 5.215
    • c = 6.584
    • Z = 2
  • Crystal Data
    • Hexagonal
    • Point group: 6mm
    • As minute imperfect rounded crystals
    • X-ray powder pattern: Synthetic (ICDD 25–815)
    • 2.66 (100), 2.61 (75), 3.29 (40), 2.137 (40), 1.863 (30), 3.72 (27), 1.707 (8)
  • Chemical Composition
    Elements Content 1
    Na2O 44.87
    CO2 [36.22]
    CaO 9.1
    SO3 4.28
    K2O 3.95
    P2O5 1.92
    SrO 0.66
    Cl 0.6
    -O = (F, Cl)2 0.31
    BaO 0.24
    F 0.4
    H2O n.d.
    Total [101.93]
  • Optical Properties
    • Optical class: [Uniaxial]
    • ω = n.d.
    • ε = n.d.
  • Estimated Properties
    Electron density Bulk density (electron density)=2.42 gm/cm3
    note: Specific gravity of gregoryite =2.46 gm/cm3
    Photoelectric PEGregoryite = 2.98 barns/electron
    U=PEGregoryite x ρelectron= 7.21 barns/cm3
    Fermion index Fermion index = 0.001419959
    Boson index = 0.998580041
    GRapi = 289.43 (Gamma Ray American Petroleum Institute Units)
    Concentration of gregoryite per GRapi unit = 0.35 (%) Estimated radioactivity from gregoryite - barely detectable

How to Identify Gregoryite

Gregoryite is a rare mineral that can be identified in the field by its white color and white streak. The density of this mineral is 2.27 gm/cm3.

Global Distribution

The only known locality of gregoryite is in Tanzania’s Oldoinyo Lengai volcano.

Occurrence of Gregoryite and Useful Mineral Associations

Gregoryite occurs as phenocrysts in lengaite carbonatite lava. It's often associated with minerals such as halite, nyerereite, alabandite, fluorite, calcite, and sylvite.





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